A backlight source applied to a liquid crystal display (LCD) is realized via two types of components—a cold cathode tube and a light emitting diode (LED). Although the well-developed and low-cost cold cathode tube technology is widely used in various types of electronic display apparatuses, an LED backlight source consumes less power than the cold cathode tube backlight source when achieving a same luminance level as that of a cold cathode tube backlight source, such that electronic display apparatuses with LED backlight sources have become publicly available. However, luminance control and associated operations of the LED backlight sources are not yet thoroughly researched in the prior art.